Submerged arc furnace with vertically movable frame

ABSTRACT

A submerged arc furnace with an open slag bath, having a vertically movable frame which is arranged above the furnace which is closed by a cover. An electrode mount and an electrode filling device are arranged on the frame. A platform is provided on which the frame is supported via at least three regulating cylinders. The platform, which is arranged above the furnace cover, is configured as a maintenance platform on which, for each electrode, there is provided a sealing unit which has components for the horizontal and vertical sealing of the free surfaces between the electrodes and the electrode passage openings of the cover.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a submerged arc furnace with open slag bath, inparticular for melting powdery batches, having a vertically movableframe which is arranged above the furnace closed by a cover. Anelectrode mount and an electrode charging device are arranged on theframe. The invention further relates to a device for sealing theelectrode passage openings in the cover of a submerged arc furnace.

2. Description of the Prior Art

Electrodes in reduction furnaces are consumed at the electrode tip andmust be charged during operation. Such a charging device for theelectrodes of electric furnaces, having a double-acting hydraulic driveconsisting of a piston/cylinder arrangement and intended for pushing theelectrodes through the contact mount is disclosed, for example, by DE AS1 440 991. The charging device which is disclosed by this document, andalso the electrode mount, are fastened on a frame which is borne by anelectrode winch. In this document, means are indicated with whichshock-free and speed-regulating charging of the individual electrodesthrough the electrode mount can be carried out uniformly during theentire lowering operation. A simultaneously controlled lowering of theelectrodes is as infrequent as a reliable sealing of the electrodepassages through the cover.

The document EP 0 093 070 B1 discloses a sealing system for electrodes,in which an annular stuffing box is pressed onto the outer surface ofthe electrode. Furthermore, a chamber is provided which encompasses theelectrode and can be loaded using compressed air. The entire sealingring is screwed fast to the furnace cover and thus cannot be easilydetached from the cover.

The document DE OS 24 55 202 discloses a main ring seal for use inconjunction with an arc furnace which has a furnace cover offire-resistant material, in which excessively filled openings areprovided. The main ring seal is supported above, and independently of,the fire-resistant furnace cover using a support structure. For thispurpose, pivotable connecting elements are used which permit a lateralmovement and an offset of the main ring seal with respect to the furnacecover. Furthermore, the main ring seal can be sealed off in relation tothe furnace cover using an adjustable cylindrically designed part. Anannular cover seal is provided on the cover and is dimensioned such thatit can be adjusted in a telecoping manner relative to the lowercylindrical part with close contact, the contact being improved furtherby means of a resilient element. This complicated construction onlypermits a cover change which involves a high degree of outlay.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide asubmerged arc furnace and a sealing device for the electrode passageopenings in the cover, both of which guarantee reliable control of theelectrode movement and with which, in a maintenance-friendly manner, anincrease in the useful operational time may be achieved.

According to the invention, piston/cylinder arrangements are connectedto the frame to which the electrode mount and the filling device arefastened. The piston/cylinder arrangements are supported on a stationaryregulating platform. Using the movement of this frame, the electrodes,as a rule 3 are used, are moved simultaneously. The filling andremounting of each individual electrode are achieved using the clampingrings in combination with the mount. The simultaneous regulation of allthree electrodes is possible in the case of submerged arc furnaces whichoperate with an open slag bath. Such furnaces are used in the processingof dusts or similar raw materials. In this case, the powdery batches arepreferably charged via hollow electrodes. The remaining chargingmaterial, predominantly coke and additives, is charged via chargingpipes onto the hot, liquid slag and floats on the slag. The slag surfaceand the batch surface have, in this case, no noticeable unevenness.

The electrode passages through the furnace cover can be designed in adust-tight or gas-tight manner. In this respect, a particular problem isposed by the thermal deformation of the cover. The present inventiontherefore a seal on the edge of the cover opening during the operationof the submerged arc furnace, which seal, at a constant force, absorbsany arbitrary movements parallel to the electrode axis and closes offthe cover opening vertically in a reliable manner.

The covers are conventionally bricked up and are subjected toincalculable wear. This results in their having to be changedspontaneously. In the case of the inventive seal of the electrodepassages, this is possible in a simple manner and in the shortestpossible time. For this purpose, the pressure cylinders which arefastened to the maintenance platform are driven back, the seal beingdetached from the furnace cover. At the same time, the electrodes aredriven out of the electrode passages. Subsequently, the free cover canbe removed using simple means and a prepared overhauled cover can inturn be placed on the furnace in a simple manner. The electrode passagesare then closed once more, the electrodes are brought into the operatingposition and production can be resumed once more.

In another embodiment of the invention, each electrode is surrounded inthe region of the sealing unit by a sealing sleeve, which is encompassedby the sealing frame. The outer surface of the sealing sleeve ismechanically worked, so that it can slide in the sealing ring frameeasily and without developing a leak. In the case of a planned coverchange, the electrode is then withdrawn into the sealing sleeve and bothare moved vertically to such an extent that their tips are located abovethe horizontal surface of the sealing flange. Then, by means ofactuating the piston/cylinder unit, the sealing unit is lifted to suchan extent that the cover can be moved horizontally freely under thelatter.

The mounting rings encompassing the electrode are designed in one piecewith the advantage of maintaining their exact shape and low wear. Therings are suspended in an insulated manner; which avoids power lossesand fulfills safety aspects for walking on the frame.

The power supply is minimized overall in terms of its length. This isalso achieved, inter alia, by means of the use of the frame and theomission of special outriggers, since the center of gravity of thecable, including the electrodes, is lower down than in the case of theconventional design.

As a result of the two-point engagement of the electrodes, namely theelectrode mount and the charging device, and the simultaneous movementof all the electrodes in the vertical direction, the electrodes are freeof lateral forces.

BRIEF DESCRIPTION OF THE DRAWING

One example of the invention is set forth in the appended drawing. Inthis case, the single FIGURE shows a detail of a submerged arc furnacewith a cover section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A vessel 11 is shown in the drawing with a cover 12 of a submerged arcfurnace 10. An electrode 71 projects into the vessel 11 through a coveropening 13.

The electrode 71 is gripped by a clamping ring 62 of a charging device60, which is supported on a frame 43 via a lifting cylinder 61.

Fastened on the frame 43 is an electrode mounting holder 52, of anelectrode mounting device 50 which includes an electrode mounting ring51, mounted to the holder 52, which likewise encompasses the electrode71.

The frame 43 is supported via a regulating cylinder 41, which isconnected to a synchronous controller 42. The cylinder 41 is mounted ona regulating and maintenance platform 31 of a maintenance unit 30. Theregulating and maintenance platform 31 in this case has a passage 32, inthe area of which there is fastened a piston/cylinder unit 33, which isconnected to a control unit 34.

The piston/cylinder unit 33 is also connected to a sealing unit 20. Thissealing unit 20 has a flange 23 which is guided parallel to the coveropening 13. An elastically deformable material 24 is provided betweenthe flange and the cover 12. It is possible to use a heat-resistantsilicon compound or a metallic compensator as the material 24. Theflange 23 is connected to a sealing frame 23, which directly encompassesthe electrode 71--as shown on the left-hand side of the figure --orencompasses a sealing sleeve 22. The use of a sealing sleeve 22 has theadvantage that defined relationships between the contact surfaces areproduced by means of mechanical working of the outer surface. Leak-tightand reliable sliding of the electrode unit during the planned coverchanges is thus guaranteed.

During a cover change, use is made of a lifting and driving unit 80,which has a lifting element 81 and a driving element 82, following thedetachment of the flanges 23 from the cover opening and the withdrawalof the electrode 71 and, if appropriate, of the sealing sleeve 22, thecover 12 is moved away from the vessel 11 without impediment.

We claim:
 1. A submerged arc furnace with open slag bath, comprising: afurnace vessel; a cover arranged on the furnace vessel and having atleast one opening therein; a vertically movable frame arranged above thevessel; an electrode mount arranged on the frame; an electrode chargingdevice arranged on the frame; at least one electrode held by theelectrode mount and the electrode charging device so as to pass throughthe cover opening at a distance from edge surfaces of the opening; amaintenance platform arranged above the cover; at least three regulatingcylinders arranged to support the frame on the platform; and, sealingmeans provided for each electrode for sealing opposing free surfacesbetween the electrode and the cover opening in both horizontal andvertical directions.
 2. A submerged arc furnace as defined in claim 1,and further comprising a synchronous controller operatively connected tothe regulating cylinders.
 3. A submerged arc furnace as defined in claim1, wherein the sealing means includes a sealing frame arranged toencompass the at least one electrode as a closed ring.
 4. A submergedarc furnace as defined in claim 3, wherein the sealing means includes asealing sleeve arranged between the sealing frame and the electrode,coaxial to the electrode, the sealing sleeve having an outer surfacewhich is mechanically worked so that it can be brought into slidingcontact with an inner surface of the sealing frame.
 5. A submerged arcfurnace as defined in claim 3, wherein the sealing means includes aflange provided on the sealing frame so as to be parallel to the cover,and a seal arranged to seal the flange against an edge of the coveropening.
 6. A submerged arc furnace as defined in claims 5, wherein theseal is made of an elastically deformable sealing material.
 7. Asubmerged arc furnace as defined in claim 6, wherein the seal is made ofa silicone compound.
 8. A submerged arc furnace comprising: a furnacevessel; a cover arranged on the furnace vessel and having electrodepassage opening; electrodes arranged to pass through the electrodepassage openings in the cover; and means for sealing the electrodepassage openings in the cover, the sealing means including a platform, asealing frame arranged to encompass and seal free surfaces of theelectrodes in a horizontal direction, a flange connected to the sealingframe parallel to the cover openings and in contact with the cover so asto seal the electrodes in a vertical direction, a piston-cylinder unitsuspended on the platform and connected to the sealing frame and theflange, and a control unit operatively connected to the piston-cylinderunit, the piston-cylinder control unit being operative to exert aconstant force on the flange when a change in height of an edge of thecover opening occurs.
 9. A submerged arc furnace as defined in claim 8,wherein the control unit is operative to actuate the piston/cylinderunit to lift the flange off the edge of the cover opening.
 10. Asubmerged arc furnace as defined in claim 9, and further comprisinglifting and driving means for moving the cover into a repair positionaway from the furnace vessel when the flange is lifted.
 11. A submergedarc furnace with open slag bath, comprising: a furnace vessel; a coverarranged on the furnace vessel and having at least one opening therein;a vertically movable frame arranged above the vessel; an electrode mountarranged on the frame; an electrode charging device arranged on theframe; at least one electrode held by the electrode mount and theelectrode charging device so as to pass through the cover opening at adistance from edge surfaces of the opening; a maintenance platformarranged above the cover; at least three regulating cylinders arrangedto support the frame on the platform; and, sealing means provided foreach electrode for sealing opposing free surfaces between the electrodeand the cover opening in both horizontal and vertical directions, thesealing means including a flange provided on the sealing frame so as tobe parallel to the cover, and a seal arranged to seal the flange againstan edge of the cover opening.